2014 Vol. 14, No. 2

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Road and railway engineering
Real-time temperature field measurement of asphalt pavement based on fiber bragg grating measuring technology
DONG Ze-jiao, LI Sheng-long, WEN Jia-yu, LENG Zhen
Abstract: Based on fiber bragg grating (FBG) measuring technology, the long-term and real-time temperature monitoring system of temperature information for asphalt pavement was established to continuously monitor asphalt pavement temperature.The temperatures of asphalt pavement layers were measured by using high-precision thermocouples to amend the FBG temperature sensors in-site.The FBG temperature sensor was used to monitor the real-time temperature of asphalt pavement.Analysis result shows that the internal pavement temperature reaches the highest value at 2:00-4:00 PM and drops to the lowest value at 4:00-6:00 AM.At 9:00-12:00 AM, the temperature grows fast and at 4:00-6:00 PM it drops fast.With the increase of asphalt pavement depth, the variation extent and rate of internal temperature decrease gradually and correspondingly, the time to reach peaks or troughs has some delays.The internal temperature of asphalt pavement varies with air temperature and keeps the same change trend with season change.The lowest temperature of asphalt pavement in the whole year appears at the beginning of January and grows gradually afterwards.More>
2014, 14(2): 1-6.
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Analysis of mechanical properties for cement stabilized asphalt pavement milling mixture
LIN Tong, KUANG Hong-zhu, HU Li-qun, JIAO Sheng-jie, SONG Shi-jie
Abstract: Six proportions of cement stabilized asphalt pavement milling mixture were designed combining the overhaul project of G108 secondary road in Weinan, Shaanxi.Based on laboratory test, the compaction properties of cement stabilized asphalt pavement milling mixture were studied.Through mechanics test of molding specimens, the influence laws of cement content, milling mixture composition, temperature and curing period on the unconfined compressive strength, rupture strength and compressive resilient modulus of mixture were studied.Analysis result shows that the maximum dry density of cement stabilized asphalt pavement milling mixture declines with the increases of milling mixture contents in surface course and base course, but the optimum moisture content increases.The compressive strength, rupture strength, and compressive resilient modulus of cement stabilized asphalt pavement milling mixture increase with the increases of curing period and cement content, but decreases with the increase of temperature.Incorporating new macadam is helpful to improve the strength and modulus of mixture.In the case of reasonable use, the strength of cement stabilized asphalt pavement millingmixture can reach 3.2 MPa, which can meet the requirement of pavement base except for over-heavy traffic.More>
2014, 14(2): 7-13.
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Orthogonal analysis of influence factors for foundation pit support approaching existing railway line
SHEN Yu-peng, WANG Hui-huang, JING Peng, TIAN Ya-hu, FU Xiao-yan
Abstract: The track level of existing railway line was taken as control standard, the influence factors including foundation pit size, existing railway line form and support form were orthogonally analyzed, and the calculation results and field settlement situation were compared. Based on the analysis methods of range and variance, the importance order of influence factors on track level approaching existing railway line was determined, and the track levels were analyzed with and without seepage.Analysis result shows that the importance order of influence factors on track level approaching existing railway line are the width of foundation pit, the subgrade height of existing railway line, the track number of existing railway line (the width of subgrade surface), the depth of foundation pit, support point position, support strength, pile length and the distance from foundation pit to slope toe.For support parameters, the first support position is dominant influence factor.When seepage is considered, the railway track level increases greatly.It is suggested to consider the width of foundation pit preferentially in construction process.The excavation approaching existing railway line should be done under sealing condition.The structure type with optimized parameters should be used to make railway track level less than 3.0 mm.More>
2014, 14(2): 14-20.
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Shallow failure stability analysis of expansive soil slope
XIAO Jie, YANG He-ping, LI Han-feng, TANG Xian-yuan
Abstract: Conventional saturated slow shear test, solidification quick shear test and quick shear test were carried out for Nanning expansive soil under low stresses condition, the change laws of various shear strengths with the change of vertical stresses were gotten, and the influences of low stresses on various shear strengths were analyzed.Residual shear strength tests were performed under the vertical stresses of 75, 100, 200 and 300 kPa, and the expansive soil slop stabilities at various shear strengths were compared by using the softwares of Seep/W and Slope/W with the consideration of rainfall infiltration and three limit equilibrium methods including M-P method, Ordinary method and Bishop method.Analysis result shows that the shear strengths are significantly influenced by the low stresses.The influences have nonlinear trends and the trends can be expressed by power functions.The saturated slow shear strength is lowest at low stress and highest at high stress.The stability analysis result of expansive soil slope calculated by nonlinear saturated slow shear at low stress is consistent with the actual slope failure situation.More>
2014, 14(2): 21-27.
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Evaluation index selection of debris flow based on entropy value theory
WANG Ying-jie, WANG Lei, RONG Qi-guo, XIONG Dong
Abstract: Aiming at solving the deficiencies of index weight determination in evaluating risk of geological disaster, the theory of minimum entropy analysis was used to form nonlinear independent components.The index optimization and weight determination were done based on their contributions to debris flow.The index weights were evaluated in the classic debris flow risk evaluation model.The evaluation results were compared with the calculated results.Analysis result shows that the main optimal indexes are the maximum rushed amount for a debris flow, frequency, basin area, main gully length, main gully bed tortuosity coefficient, vegetation coverage, the reserve of loose solid material, basin cutting density and sediment supply length ratio.The corresponding weight values of these indexes are 0.235 3, 0.235 3, 0.079 1, 0.079 1, 0.079 1, 0.079 1, 0.073 0, 0.073 0 and 0.073 0 respectively.The numbers of extreme, heavy, moderate and slight debris flows are 3, 3, 6 and 0 respectively.The calculated results are consistent with the real situation and development trend of studied debris flow area.It proves thereasonability of minimum entropy analysis theory applied in geological disaster risk evaluation.More>
2014, 14(2): 28-33.
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Transportation vehicle engineering
Air-pumping effect analysis for brake disc of high-speed train
ZUO Jian-yong, LUO Zhuo-jun
Abstract: To study the air-pumping characteristics of brake disc during train operation, the finite element models including vehicle, rail, brake disc and related air flow field were put forward. The air-pumping power consumption of brake disc was calculated, and its effect on traction power was analyzed by using dynamic grid and flow-solid conjugation simulation method.Taking a 8-unit high-speed train composed of 4 motor cars and 4 trailers running at 300 km·h-1 as an example, the air-pumping effect of brake disc was simulated and compared.Simulation result indicates that the air-pumping power consumption of brake disc is in proportion to train running speed.The air-pumping power consumption of each car is about 54-70 kW.The air-pumping torque, independent of installation position of brake disc, is mainly influenced by the rotational velocity of brake disc.The proportion of air-pumping power consumption of brake disc reduces with the increase of train running velocity.When train running velocity increases from 200 km·h-1 to 400 km·h-1, the proportion of air-pumping power consumption reduces from 12% to 8%. Blocking air from the inlets of brake discs is helpful to reduce the influence of air-pumping power consumption.Taking the train running at 300 km·h-1 as an example, when the inlets of brake discs are blocked, the air-pumping power consumption of brake disc reduces from 489 kW to 68 kW, the basic resistance power consumption consumed by air-pumping power consumption reduces from 9.0% to 1.3%, so the method is effective.Obviously, it has greater realistic meanings for the cooling rib structure optimization of brake disc of high-speed train in considering the air-pumping power consumption issue.More>
2014, 14(2): 34-40.
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Influence of cornering stiffness of straddle-type monorail running wheel on tire wear under curve negotiating
WEN Xiao-xia, DU Zi-xue, ZUO Zhang-yong, LIANG Zhi-hua, ZHAO Da-yi
Abstract: Based on vehicle tire wear theory, the influences of cornering stiffness of running wheel on the cornering force of running wheel and the radial forces of guide wheel and stabilizing wheel for monorail vehicle were analyzed.When monorail vehicle ran along curve track, the changing trend of running wheel's friction power consumed with cornering stiffness variation was studied. Analysis result shows that affected by the radial forces of guide wheels and stabilizing wheels, the cornering force of running wheel increases as its cornering stiffness increasing. When the cornering stiffness range of running wheel is from 1 kN·rad-1 to 120 kN·rad-1, its cornering force and side slip angle are linear, and side slip angle has minor change.When the cornering stiffness exceeds 120 kN·rad-1, side slip angle increases rapidly into the nonlinear region.Based on tire wear index, with the cornering stiffness increase of running wheel, its tire wear increases at 1.2% rate as curve traveling.The cornering stiffness also affect the curve negotiating performance of monorail vehicle, much small cornering stiffness is not conducive to form shook head torque and the curve performance is bad.In order to reduce tire wear, the recommendeddesign cornering stiffness of running wheel is 9.37 kN·rad-1 under the condition of good curve negotiating performance.More>
2014, 14(2): 41-48.
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Review of pantograph active control
LU Xiao-bing, LIU Zhi-gang, SONG Yang, HAN Zhi-wei
Abstract: In order to control pantograph-catenary coupling vibration and improve the current collection quality of high-speed train, the modeling of pantograph-catenary system, the control objectives and the measurement system, the control algorithms, the actuator and its installation, and the experimental verification were reviewed in the active control of pantograph.The impact of pantograph-catenary model on the computation precision and time in contact force simulation, the advantages and disadvantages of different control algorithms and the choice methods of operating mechanism were commented.The future research directions of active control were prospected from model optimization, algorithm design, signal modification and some other aspects.Analysis result shows that in the active control of pantograph, the key factors of pantograph-catenary system and the calculation efficiency must be considered in pantographcatenary modeling, the control target should reflect current collection quality, measurement system should decrease the influence of locomotive disturbance on the reliability of measurement result, and control mechanism can not impact the work of hoisting mechanism.The critical factors that decide pantograph-catenary system to be successfully applied in actual engineering are real-time control algorithms and high-efficiency actuators.More>
2014, 14(2): 49-61.
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Scanning measurement method of buttock contour line at ship bottom
WU Jun, DING Shen-qi, YU Kui, LI Xiao-biao, MA Xi-qin
Abstract: The single-point measurement principle of buttock contour line at ship bottom was analyzed.Acoustic measurement components were used to measure several draught points through reciprocating scanning, various parameters including ship sailing speed, scanning distance and scanning speed were effectively processed, and a new measurement method of buttock contour line at ship bottom based on single-beam sonar sensor was proposed.The acoustic receiving area was taken as constraint condition, the judgement criterion of ship bottom edge was carried out, the reconstruction formula of buttock contour line at ship bottom was deduced, and simulation test was carried out by using small scaled ship model.Test result shows that when ship sailing speed is 2 cm·s-1, 19 contour points are measured, the draughts of ship bow and poop are 2.91 and 3.09 cm respectively, and the trim is 0.18 cm.When ship sailing speed is 4 cm·s-1, 10 contour points are measured, the draughts of ship bow and poop are 2.79 and 3.15 cm respectively, and the trim is 0.36 cm.All the measured point data are of good consistency, and the sailing attitude is consistent well with the actual state.More>
2014, 14(2): 62-67.
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Effect of load transfer of tractor-semitrailer on cornering braking stability
LI Chen, LI Xing-hu, ZHOU Wei, ZHANG Hong-wei
Abstract: A cornering braking dynamics model of tractor-semitrailer was established.Its accuracy was verified by comparing its outputs with the test data of tractor-semitrailer.By the model simulation of cornering braking process, the changes of vertical loads on coaxial left and right wheels were analyzed, and their effects on wheel locking order and braking stability were carried out.The effect of brake chamber's pressure increase on cornering braking stability was studied. Simulation result indicates that when the maximum braking pressure is 0.62 MPa, the right wheel vertical load of tractor steering shaft increases from 12.00 kN to 23.00 kN, but the left wheel vertical load decreases from 12.00 kN to 0.66 kN, so load transfer is significant.When the maximum braking pressure increases, the load transfer obeys the same regulation, which affects the locking trends of coaxial left and right wheels and the work time of ABS.When the maximum braking pressure increases from 0.62 MPa to 1.50 MPa, the folding angle of tractor-semitrailer decreases from 0.73 rad to 0.67 rad, so the cornering braking stability improves.More>
2014, 14(2): 68-74.
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Transportation planning and management
Optimal model of taxi waiting time fee under traffic congestion condition
YUAN Zhang-wei, MI Xue-yu, WU Qun-qi, WEI Da-li
Abstract: Based on economics demand theory, taxi income was divided into starting fee, mileage fee and waiting time fee.Taxi capacity was taken as constraint condition, the influence factors of taxi income during peak period and non-peak period were considered, the influence levels of waiting time fee on taxi demand and income were analyzed, and the optimal model of taxi waiting time fee under traffic congestion condition was set up.Based on the actual situation of taxi market in Beijing City, the example verification was carried out by using three schemes including original scheme, adjustment scheme and proposed scheme.Analysis result shows that when the starting fees are 12, 14, 12 yuan, unit mileage fees are 2.0, 2.3, 2.0 yuan·km-1 and waiting time fees are 24.0, 55.2, 55.2 yuan·h-1, taxi incomes are 669.9, 504.9, 675.9 yuan respectively. Under adjustment scheme, taxi demand decreases by 46.1%, and taxi income decreases by 25%. Under the proposed scheme, taxi demand decreases by 18.5%, and taxi income keeps stable level compared with original scheme.According to the exist structure of taxi fee, the adjustment objective of taxi demand and income can be realized by using proposed scheme.In the reformscheme of taxi price in Beijing City, it is suitable to keep or decrease starting fee and mileage fee and increase waiting time fee.More>
2014, 14(2): 75-81.
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Pre-examine method of traffic congestion under urban land redevelopment
WANG Yan-li, DONG Zhi, WU Bing, LI Lin-bo
Abstract: Based on systematic analysis method, the evaluation index system of traffic condition and congestion level was set up.Two indexes including road network traffic congestion ratio and road network traffic congestion contribution were used to evaluate the impact level of traffic congestion, the judgement standard of traffic reasonability was determined, the pre-examine method of traffic congestion under urban land redevelopment was established, and example verification was carried out by using three development schemes of partial regions in Maryland including no-redevelopment scheme, housing redevelopment scheme, housing and employment redevelopment scheme.Analysis result shows that in the first scheme, car sharing ratio, average trip distance, total running mileage, total running time, total vehicle delay, congestion lane mileage, vehicle delay index and congestion lane mileage ratio are 93.70%, 24.98 km, 225 817 698 km, 5 369 291 h, 2 038 880 h, 4 686 km, 0.380 and 0.180 respectively.In the second scheme, these indexes are 92.48%, 24.78 km, 219 992 101 km, 5 227 303 h, 1 831 190 h, 4 320 km, 0.350 and 0.166 respectively.In the third scheme, these indexes are 92.22%, 24.82 km, 219 023 166 km, 5 342 457 h, 2 062 041 h, 4 422 km, 0.386 and 0.169 respectively.The road network traffic congestion ratios of these three schemes are 0.280, 0.258, 0.278 respectively.In the third scheme, vehicle delay and vehicle delay index both rise.It is clear that the second scheme is slightly helpful to reduce traffic congestion and better than the first and third schemes.More>
2014, 14(2): 82-89.
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Traffic information engineering and control
Handoff model of operation control system of high-speed maglev based on DSPN
CAO Yuan, ZHANG Yu-zhuo, MA Lian-chuan, SUN Ya-qing, MU Jian-cheng
Abstract: Considering the factors of the communication outage of 38GHz millimeter wave and channel occupancy, deterministic and stochastic Petri nets model (DSPN) was developed based on the handoff process of maglev operation control system.The structures of single mobile terminal (MT) and redundant MT were compared.The effects of base station interval and train running velocity on the handoff reliabilities of single MT and redundant MT were investigated.Investigation result indicates that the handoff performance of redundant MT is significantly higher than that of single MT, the parking probability of single MT is approximate 3×104 times of that of redundant MT.The handoff success rate reduces with the increase of train running velocity and the decrease of base station interval.In the special case, in which the train running velocity is 500 km·h-1 and the base station interval is 500 m, the handoff success rates of redundant MT and single MT are only 98.50% and 97.85% respectively. Research result provides basis for the QoS optimization of train-ground communication subsystem in maglev operation control system and mobile cell setting.More>
2014, 14(2): 90-96.
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Web multidimensional digital waterway monitoring platform
PAN Ming-yang, LIU Tao, WANG De-qiang, ZHAO De-peng, ZHANG Xin-yu
Abstract: Based on two-dimensional electronic navigational chart (ENC) and three-dimensional waterway model, a new web multidimensional digital waterway monitoring platform was proposed.The architecture of the platform was designed based on Java.In order to enhance the rendering speed of the platform, quadtree-based spatial data organization and data prefetching strategy were applied to optimize the multidimensional waterway model.In order to implement large scale waterway dynamic monitoring, the organization, access, display and query of dynamic information of ships and buoys in waterway were researched, and a binary thinning based rendering algorithm of dynamic object layer and a ray casting based picking operation of dynamic object in 3D space were proposed.Test result shows that the platform operates steady and smooth.Through the web, the platform can display three dimensional waterway's terrains, wharf facilities, buildings and two dimensional ENCs in a unified multidimensional framework, and monitor the real-time dynamic states of all vessels and buoys in waterway.More>
2014, 14(2): 97-103.
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Wireless network testbed oriented internet of vehicles
DUAN Zong-tao, KANG Jun, TANG Lei, LU Ming-ming, WANG Dong, WANG Chao
Abstract: Considering the features of rapid mobility and realizing way diversity of tested nodes in the internet of vehicles, a wireless network testbed oriented internet of vehicles was designed and implemented by using network tomography technology.The testbed was composed of network performance measurement units and up-down stream detection units of testing area.The impact of rapid mobility of test vehicle on network performance was tested by designed testbed.The performance indexes were composed of round-trip delay, packet loss rate, average throughput, etc.in the network.Test result indicates that wireless network performance indexes degrade with the increase of the average speed of test vehicle in the internet of vehicles.When the average speed of test vehicle is more than 70 km·h-1, all performance indexes decrease significantly comparing to the situation of 20 km·h-1.Average network round-trip delay increases about 2.4 times, packet loss rate increases about 10 times, and average throughput decreases about 2.6 times.Obviously, the wireless network performance indexes of internet of vehicles are measured and evaluated effectively by the designed wireless network testbed oriented internet of vehicles.More>
2014, 14(2): 104-111.
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Research status and development of transportation data standards
ZHANG Shao-yang, GE Li-juan, AN Yi-sheng, CAO Jin-shan
Abstract: The compilation and management statuses of transportation data standards in China were analyzed. Transportation data standards were divided into 4 categories, including management standard, data definition standard, exchange standard and interface implementation standard.The standardization demands were analyzed and contrasted with the existing standards from the aspects of data producing, storage, exchange and application.Research status and deficiency of transportation data standards were discussed from management and overall planning, data definition, data storage, data exchange and decision support application.Analysis result indicates that in present standard management and overall planning, the bottom-up compilation and respective responsibility of informatization professional standard committees (IPSCs) lead to overlap of IPSCs and insufficient of overall planning research.In terms of data definition standards, the existing basic standards put too much emphasis on meeting the needs of application systems, causing the inadequacies of fundamentality of basic standards and the lack of data definition standard system.In terms of data storage, the setting of data storage standards is still blank.In terms of data exchange, the internal standards of each business system are alreadymade, but a systematic and opening mechanism for sharing and exchanging is still not established.In terms of decision support applications, decision support method for accurate data and large data is shortage.It is suggested that traffic information basic standard workshop should be set up to enhance the overall planning research and collaborate with the different IPSCs in management.In standard construction, the top-level design should be enhanced.Meanwhile, the research of transportation decision support method should be strengthened.More>
2014, 14(2): 112-126.
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